Stress problems are very common. The American Psychological Association's 2007 "Stress in America" poll found that one-third of people in the United States report experiencing extreme levels of negative stress. In addition, nearly one out of five people report that they are experiencing high levels of negative stress 15 or more days per month. Impressive as these figures are, they represent only a cross-section of people's stress levels at one particular moment of their lives. When stress is considered as something that occurs repeatedly across the full lifespan, the true incidence of stress problems is much higher. Being "stressed out" is thus a universal human phenomenon that affects almost everyone.

What are we talking about when we discuss stress? Generally, most people use the word stress to refer to negative experiences that leave us feeling overwhelmed. Thinking about stress exclusively as something negative gives us a false impression of its true nature, however. Stress is a reaction to a changing, demanding environment. Properly considered, stress is really more about our capacity to handle change than it is about whether that change makes us feel good or bad. Change happens all the time, and stress is in large part what we feel when we are reacting to it.

We can define stress by saying that it involves the "set of emotional, physical, and cognitive (i.e., thought) reactions to a change." ...